1. Field of the Invention
The present invention relates to an antenna apparatus transmitting and/or receiving radio waves, for example, a transmitting antenna apparatus for providing a trigger to a transmitting apparatus (transmitter) mounted on a wheel triggering the transmitting apparatus to cause it to transmit an ID number of a tire having the transmitting apparatus mounted therein and various types of tire information including an air pressure of the tire, and to a communication method employing it.
2. Description of the Related Art
Recently, a monitoring system for monitoring a state of a tire (typically, an air pressure of the tire) upon running has been proposed. This monitoring system includes a transmitter mounted in each wheel as well as an on-vehicle monitoring apparatus including a receiver provided in a vehicle cabin. The on-vehicle monitoring apparatus receives, via the receiver, various types of tire information including an air pressure of the tire transmitted from the transmitter. Then, based on the various types of tire information, the on-vehicle monitoring apparatus provides various types of information to a driver, if necessary, i.e., an alarm, for example, a message ‘an air pressure of front-left wheel lowers’.